London 2012 organisers have promised to provide a detailed breakdown of the final batch of 1.3m tickets that will be made available next month, to help prospective purchasers choose which to apply for.

The organising committee and its partner Ticketmaster are under pressure to deliver following technical issues and controversies that have dogged the ticketing process amid huge demand.

"When we do our ticketing process in April, we'll tell people exactly how many tickets are available," said the Locog chief executive Paul Deighton.

Around 20,000 people who thought they had secured tickets in the second round of sales but were subsequently let down have been given a 24-hour window to buy tickets. After that, the remaining 1m or so who missed out in the first phase will be given five days to apply on a first come, first served basis.

But not all the tickets for all sessions will be made available at once and Deighton promised it would be clear exactly how many would be on offer for each session in every sport to help prospective purchasers plan their buying strategy.

Deighton, who along with the chairman Lord Coe will face the London Assembly members who have been critical of the transparency of the ticketing process, will continue to resist requests to break down the percentage of tickets sold to the public for each session so far.

"The debate has been had. I'm not sure there's any more to say. We're not going to give any estimates before we're completely clear which tickets we've sold to whom and we can give a complete picture," he said. "We're not going to give a running commentary after each sale, because it creates a misleading picture. I don't like putting out numbers based on assumptions and estimates."

With hundreds of thousands of tickets likely to be on sale at public box offices in the run-up to the Games, in practice that means the final breakdowns will not be available until after the Olympics.

Deighton, speaking at a Locog event to highlight diversity and inclusion policies that were praised by the equalities minister Lynne Featherstone, said he was confident the crowds at the Games would reflect London's population and not have a white, middle class bias.

"One of the reasons we saw such huge demand was because there was an awful lot of cheap tickets. By the time we've finished this, more than 2.5m tickets will have gone for £20 or less. That's a very big chunk of them. People who normally wouldn't be able to get tickets had a chance to do that," he said.

"The final few hundred thousand tickets we're able to identify right at the end, there will be some box office stuff as well that will have a natural advantage for the local community. If the test events are anything to go by, I think we've got a decent balance in there."

He said the cycling and diving test events highlighted the extent to which the crowd would "reflect the fact it's the world's biggest international event".

Of the 8.8m tickets, 6.6m have been made available to the British public but for some of the most high profile events just over a third of those present will have received tickets reserved for the public. Deighton argued that, once sponsors tickets given away to the public and tickets sold in Europe to British buyers had been taken into account, the proportion would be much higher in practice.

The final batch of 1.3m tickets will be for all sports except synchronised swimming, which was the first event to sell out following an embarrassing error where the tickets were over-sold. There are also still around 1.5m football tickets remaining, which will be marketed in earnest once the draw is made.